The objective of this project is to develop an understanding of the relationship between dietary protein intake and blood pressure regulation. The specific aims are: 1) to examine the effects of dietary protein alteration on the development and maintenance of genetic hypertension in rats, 2) to evaluate the modulation of norepinephrine release in the isolated portal vein and perfused-superfused caudal artery of the rat before and after the development of hypertension and determine if alterations in dietary protein are reflected as changes in activity of alpha2 receptors, and 3) to determine if alterations in dietary protein change the blood pressure and heart rate responses to sympathetic stimulation of the entire spinal cord. The hypothesis that inhibitory alpha2 receptor sensitivity is altered by protein intake will be examined in genetically hypertensive rats. Since a reduction in protein intake in rats has been associated with reduced alpha adrenergic vasoconstrictor responses, as well as enhanced turnover of norepinephrine, protein intake may be an important determinant of alpha adrenergic receptor ontogeny. There is evidence that alpha2 receptor sensitivity changes play a role in the development and maintenance of genetic hypertension. Using low, medium-low, and normal protein diets, the release, uptake, and content of norepinephrine will be examined in blood vessels of genetically hypertensive animals and controls. In addition, sensitivity to alpha2 antagonism will be assessed using yohimbine. Blood pressure will be measured directly and indirectly during the course of the study. This investigation will allow insight into dietary influences on blood pressure regulation and neurotransmitter dynamics and will provide information necessary for the pursuit of alternatives to traditional pharmacological approaches in hypertension.